Pros: PORTABLE. Good quality subwoofer speaker. Amplified. Can be connected to any audio system.
Cons: "BOOM, BOOM, BOOM" sound may not be for those more critical. Lacks auto on/off feature.
I owned the Sharper Image SA-251 subwoofer. I bought it re-manufactured from Sharper Image for around $20. At that price it was worth it. Personally, I would not pay the full price of $99 for it, especially after owning one myself.
This unit is ok, but has several good and bad points.
It is portable. It has a recessed handle built-in to the top of the unit.
It is lightweight. It can be easily carried from room to room, which is not so easy with most subwoofers.
It is a powered subwoofer, which means it incorporates its own discrete amplifier. You can therefore plug this subwoofer into basically any audio system featuring a subwoofer output jack or even a simple line-out jack. When plugging this unit into a standard left/right line-output jack, you may want to buy a "Y" cord which converts two mono line-outputs into one line-output. That way you won't lose any bass signals.
Adjustable Volume control on the subwoofer. This is a nice feature. You'd be surprised at how many big name home theater systems do not include such feature on their packaged subwoofers.
Woofer driver is approx 5.5 inches in diameter. While somewhat small, it is of very good quality I must say. The suspension is a large rubber roll type and the cone exhibits a lot of cone excursion which translates into more deep bass with less distortion. I was really impressed with the quality of the subwoofer speaker itself.
Amplifier power is adequate. It will not rattle the windows, but it delivers a lot of bass for its size. Again, I was very impressed.
What didn't I like about it.
Well, it doesn't have an automatic on/off switching circuit. Most subwoofers have a built-in sensor which detects signals being sent to it and then the subwoofer will turn itself ON. When it is OFF, it is usually in STANDBY mode. With this subwoofer, you have to constantly bend down and actually push in the ON button. It's not a big deal, but I much prefer the auto switching circuit.
The ON circuit does not have any delay. That is, when one turns on a decent quality amp, receiver or subwoofer, the amp usually features a few second delay to protect the speakers and amplifier circuitry. This subwoofer simply comes ON with a loud "thud" sound. Again, not a bid deal, but I prefer the delay circuitry.
This subwoofer may impress the novice, but sounds rather "boomy" to me. Bass sounds are very full and pretty deep, but the "boom" effect loses it for me. The plastic cabinet may be part of the problem as well as a lack of damping material within the enclosure itself. Even the cyndrical shape of the cabinet may contribute to the boominess of this subwoofer. It's too bad, because the actual subwoofer driver is of quite good quality.
I used my SA-251 while I owned my Fisher SLIM2000 and my Sharper Image SA-260. When used in conjunction with those systems, I was able to derive a pretty good sounding system for a small price. I paid less than $100 for a re-manufactured SA-260 and only $20 for the sub as stated above.
I like the idea of portability. with one of the systems named above and this subwoofer, I could actually carry my whole sound system from room to room, house to garage to patio, etc. So, it is very useful if you are into music as I am. With the subwoofer included, such a system can play quite loudly and be heard well even when used outside in the daytime, when your audio system is most taxed due to the noise level of the outdoors and the lack of reflective walls and surfaces.
Most subs are not portable. So this sub is somewhat unique.